機器自己運作
最原本的用法：人只負責裝好、按下開始，之後每一步是機器自己接下去。
self-operating · adjective · B2
Working by itself, without a person needing to control each step.
自動的
核心畫面
Picture the moment after someone lets go. A door with a spring closes on its own; nobody is pushing it. Something set up beforehand is now running the next step, so the human hand is out of the picture — not because the person is absent, but because their choosing is no longer part of it. Every use of `automatic` is that same missing hand: in a machine, in a rule, in a habit.
automatic 可以想成「手放開之後」的那一刻。裝了彈簧的門自己關上，沒有人推它；事情之所以繼續走下去，是因為有…更多收起
automatic 可以想成「手放開之後」的那一刻。裝了彈簧的門自己關上，沒有人推它；事情之所以繼續走下去，是因為有人事先把它裝好了，所以現在這一步不需要有人再決定一次。人不見得不在場，只是他的「選擇」已經不參與了。機器、規定、習慣，這個字用在哪裡都是同一隻消失的手。From the word’s history
From Greek automatos, autos "self" plus a root meaning "thinking, animated" — literally acting of itself. English took the adjective in 1812 for things "self-acting"; the machinery sense follows in 1850, and the nouns are recent: automatic weapon 1902, car with automatic transmission 1949.
automatic 來自希臘文 automatos：autos 是「自己」，後半的字根有「會動、有心思」的意思，合起來就是「自己動起來」。英文 1812 年借來當形容詞，指「自己會動的」；1850 年才專指機器，名詞用法更晚——自動武器 1902 年，自排車 1949 年。所以「不用人動手」一直是這個字的中心，後面的意思只是換了場景。
Online Etymology Dictionary, entry "automatic" (etymonline.com/word/automatic)
Four branches
規定一觸發就跟著發生
把機器換成制度，畫面完全一樣：條件一達成，結果就自己跑出來，沒有人在中間點頭或搖頭。
guaranteed result · adjective · B2
Certain to happen as a direct result of something, especially because of a rule or law.
必然的
身體自己做出來
這次自己動的是人。同一個動作做了幾千次之後，念頭那一段被跳過了，身體像機器一樣直接接上去。
reflexive, unthinking · adjective · B2
Done without thinking about it, usually because you have done it many times before.
反射性的
以自動機構命名的東西
形容詞用久了，形容詞自己就變成那個東西的名字：不用再說 an automatic gun 或 an automatic car，直接說 an automatic，聽的人從場景就知道是哪一種。
automatic weapon · noun · B2
A gun that keeps firing one shot after another while the trigger is held.
自動武器
原始詞典資料9 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
automaticadj/ˌɔː.təˈmæt.ɪk/
- 1
Capable of operating without external control or intervention.
- The automatic clothes washer was a great labor-saving device.
- "But you know of the automatic card-player?" […] Carrados had heard more than once casual allusions to a wonderful mechanical contrivance that played cards with discrimination.
- 2
Done out of habit or without conscious thought.
- The reaction was automatic: flight!
- Absent-minded doodling is a form of automatic art.
- 3
Necessary, inevitable, prescribed by logic, law, etc.
- Spitting at another player means an automatic red card.
- 4
Firing continuously as long as the trigger is pressed until ammunition is exhausted.
- Fully automatic weapons cannot be legally owned by private citizens in the US, except in very special circumstances, as by private security companies.
- 5
An autoloader; a semi-automatic or self-loading pistol, as opposed to a revolver or other manually actuated handgun, which fires one shot per pull of the trigger; distinct from machine guns.
- The US Army adopted John Browning's M1911 pistol as its sidearm, chambered in .45 ACP (Automatic Colt Pistol).
- From a little hand-bag he extracted his automatic pistol, which he put upon the mantelpiece.
- 6
computingengineeringmathematicsAutomatically added to and removed from the stack during the course of function calls.
- Automatic variables are created on the stack. They are valid only from the point where they are declared to the end of the function.
- 7
mathematicssciencesHaving one or more finite-state automata.
automaticnoun/ˌɔː.təˈmæt.ɪk/
- 1
A car with an automatic transmission; the transmission itself.
- I never learned to drive a stick. I can only drive an automatic.
- 2
A semi-automatic pistol.
- The G-men raiding the speakeasy were equipped with .45 automatics, while the local policemen were carrying revolvers and shotguns.
- "I told him that if my automatic was not a spook-stopper, nothin' else would serve."
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。